Transmission cover with improved airflow

ABSTRACT

A cover for a transmission having improved airflow path is disclosed. The interior of the cover has a progressively narrowing airflow path to reduce pressure drop through the cover, thereby improving the cooling efficiency of the airflow through the cover. The cover includes a diverter sheltering the air inlet to the cover to prevent air in the cover from exerting outward pressure on the incoming air.

PRIORITY CLAIM

The present application is a continuation of U.S. application Ser. No.15/179,920, entitled TRANSMISSION COVER WITH IMPROVED AIRFLOW, filedJun. 10, 2016, which is a continuation of U.S. application Ser. No.13/948,007, entitled TRANSMISSION COVER WITH IMPROVED AIRFLOW, filedJul. 22, 2013, and issued as U.S. Pat. No. 9,366,331 on Jun. 14, 2016the content of which is hereby incorporated by reference.

FIELD OF INVENTION

This invention relates generally to a case for a vehicle transmissionsuch as a continuously variable transmission (“CVT”) with an improvedairflow path.

BACKGROUND OF THE INVENTION

All-terrain vehicles (“ATVs”) and recreational off-road vehicles(“ROVs”) generally feature CVTs to transmit power from the engine to thewheels. Like other moving parts of the vehicle, transmissions tend togenerate heat during use that, if left unchecked, can be harmful tocomponents of the engine. CVTs in particular generate heat due to thebelt sides scrubbing against the sides of the sheaves anytime they areengaged and moving. CVTs are conventionally cooled by moving externalair into the CVT cover and over the hot components and out of the cover.However, due to the rapid motion within the CVT cover and the intensespace constraints in an engine and transmission, proper airflow is notalways achieved efficiently. There is a demand in the art for improved,efficient cooling features for engines generally and specifically forCVTs.

SUMMARY OF THE INVENTION

The present invention is directed to a cover or case for a transmission.The transmission can be a CVT or another suitable transmission having adrive shaft and a driven shaft. The cover includes a first hole foraccommodating one of the drive shaft or the driven shaft of thetransmission and a second hole for accommodating the other one of thedrive shaft and driven shaft. The cover has a lateral dimension measuredin a direction parallel to the shafts, and a line passing between centerpoints of the first and second holes separates the cover into a firstside and a second side. The cover also has an air inlet near the firsthole and an air outlet near the second hole. The cover has a deep regionnear the air inlet, a ramp region adjacent to the deep region, and ashallow region adjacent to the ramp region. The deep region has a largerlateral dimension than the shallow region and the ramp region slopesbetween the deep region and the shallow region. The deep region, rampregion, and shallow region are on the first side of the cover. Airflowthrough the cover is directed to pass into the air inlet, over the deepregion, ramp region, and shallow region before exiting the cover. Thecover also includes a high region between the air outlet and air inleton the second side of the cover, having a smaller lateral dimension thanthe shallow region. A portion of the air from the shallow region passesover the high region before joining the incoming airflow at the inlet.The cover also has a ridge between the first and second holes andseparating the ramp region and the high region and a diverter betweenthe high region and the air inlet and positioned to prevent air from thehigh region from exerting pressure on the incoming airflow.

Other embodiments of the present disclosure are directed to a cover fora transmission having a drive gear and a driven gear rotatably coupled.The cover includes a first end configured to accommodate the drivengear, a second end opposite the first end configured to accommodate thedrive gear, and a middle section between the first and second ends. Thefirst end, second end, and middle section together form an oval“racetrack” path for airflow. The cover also has an air inlet and an airoutlet opposite the air inlet. Air introduced through the air inletmoves around the racetrack path. A portion of the air leaves the coverthrough the air outlet and a portion of the air cycles around theracetrack path. A first portion of the racetrack path between the airinlet and air outlet is wider near the air inlet and becomesprogressively narrower between the air inlet and the air outlet, and asecond portion of the airflow path between the air outlet and the airinlet is narrower than a narrowest region of the first portion of theracetrack path. The cover also includes a diverter extending from thesecond flow path over the air inlet to prevent air from the secondportion of the flow path from exerting pressure onto air introduced tothe cover through the air inlet.

In still further embodiments, the present disclosure is directed to atransmission including a drive gear, a driven gear, and means forrotatably coupling the drive gear to the driven gear to transmit powerfrom the drive gear to the driven gear. The transmission is held withina cover surrounding the drive gear and driven gear. The cover has anelliptical shape to accommodate the round shape of the drive gear andthe driven gear, an air inlet configured to direct air into the cover tocool the drive gear and driven gear, and an air outlet configured torelease air from the cover after cooling the drive gear and the drivengear. The cover has a lateral interior dimension measured betweeninterior walls of the cover measured in a direction parallel to the axesof rotation of the drive gear and driven gear. The air inlet and airoutlet are positioned to direct the air to circulate around the interiorof the cover in a racetrack path defined by the elliptical shape of thecover, the racetrack path having a first segment between the air inletand air outlet on a first side of the cover and a second segment betweenthe air outlet and the air inlet on a second side of the cover. Thelateral dimension of the cover on the first side of the cover is widestat the air inlet, narrowest at the air outlet, and ramps from wide tonarrow between the air inlet and air outlet. The lateral dimension ofthe cover on the second side of the cover is narrower than a narrowestpoint of the first side of the cover. The cover also has a diverterextending from the second side of the cover over at least a portion ofthe air inlet to prevent air moving over the second side of the coverfrom exerting pressure on incoming air in the air inlet.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred and alternative embodiments of the present invention aredescribed in detail below with reference to the following drawings.

FIG. 1 is a partially cut-away view of a CVT according to embodiments ofthe present disclosure.

FIG. 2 is an interior view of a portion of the CVT cover according toembodiments of the present disclosure.

FIG. 3 is an interior view of a portion of the CVT cover according tofurther embodiments of the present disclosure.

FIGS. 4A-E illustrate CVT cover alternate embodiments.

FIG. 5 is a block diagram of a vehicle that includes an engine, surfaceengaging members, and the CVT cover according to embodiments of thepresent disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a partially cut-away view of a CVT 100 and a CVT cover 110.The CVT 100 has a driven clutch 101, a drive clutch 102, and a belt 103between the driven clutch 101 and the drive clutch 102. The drive clutch102 is coupled to the engine crankshaft (not shown), receives power fromthe engine, and transmits the power through the belt 103 to the drivenclutch 101, and eventually from the driven clutch 101 to the wheels (seethe engine and surface engaging members of the vehicle shown in FIG. 5).The drive clutch 102 can have two conical sheaves 104 holding the belt103 between them. Moving the sheaves 104 toward and away from oneanother changes the effective gear ratio of the drive and driven clutchsystem. As the sheaves 104 of the drive clutch 102 move farther apartthe belt drops to a lower location on the sheaves 104 and to a higherlocation on the sheaves of the driven clutch 101. Conversely, as thedrive sheaves move closer together, the driven sheaves mover fartherapart. Thus, the gear ratios from input to output smoothly change,thereby achieving a continuously variable transmission. Although, allthe movement of the belt sides along the sides of the sheaves as theclutches are turning creates heat. The belt can only withstand so muchheat before it fails under a load. Aspects of the present invention canalso be used with other transmissions and with other engine casingcomponents.

The backside (first portion 116) of CVT cover 110 surrounds the side ofthe CVT 100 adjacent the engine and transmission and protects the movingparts. The cover 110 also serves as a channel through which air moves tocool the sheaves and belt. The cover includes an air inlet 112 near thedrive clutch 102 and an air outlet 114 near the driven clutch 101. Thepositions of the air inlet 112 and outlet 114 can vary slightly, butpreferably the air inlet 112 and outlet 114 are on substantiallyopposing sides of the cover 110 to permit the air to flow over thecomponents of the CVT 100 and out the other side. The cover 110 isformed of two portions: a first portion 116, and a second portion 118.The two portions 116, 118 are split along a line parallel with the beltand are held together by bolts through bosses 120 around the peripheryof the cover 110. The bosses are preferably on the external portion ofthe CVT cover 110 to allow smoother air flow in the interior of thecover for better cooling. The first portion 116 can be on the engineside and the second portion 118 can be on the wheel side, or vice versa.In the illustrated embodiment, the first side 116, in which the airinlet 112 and air outlet 114 are formed, are both on the engine side ofthe CVT 100. Depending on the configuration of the CVT 100 and engine,the heat builds up more significantly on the engine side of the CVT 100.However, in a different configuration, the heat may be more concentratedelsewhere, in which cover the air inlet 112 and outlet 114 can bepositioned accordingly. The air inlet 112 and outlet 114 are alsopreferably located where a fan can pull air into the cover. In thiscase, the fan is convenient to situate on the engine side of the driveclutch sheaves 104. The fan moves air into the cover and towards theoutlet 114.

FIG. 2 is an interior view of the first portion 116 of the CVT cover 110according to embodiments of the present invention. The first portion 116has two holes 122, 124 to accommodate the shafts of the drive clutch 102and the driven clutch 101, respectively. The clutches 101, 102 turnclockwise as shown by arrows A. The cover 110 has an inlet end 126 nearthe inlet 112 and an outlet end 128 near the outlet 114. The cover 110is generally rounded at the ends 126, 128 and somewhat straight in themiddle. In some embodiments the inlet end is slightly smaller than theoutlet end 128 because the drive clutch 102 is smaller; however, inother embodiments their relative sizes can vary to accommodate the sizesof the driven clutch 101 and drive clutch 102. The air path through thecover 110 therefore starts at the inlet 112, moves into the inlet end126 and then along a lower region 130 of the cover 110. Some of the airwill rotate around the drive clutch, but the majority of the air ismoved into contact with the driven clutch following the rounded interiorshape of the outlet end 128 and eventually into the outlet 114 and outof the cover 110.

The lateral dimensions of the cover 110 are defined as a distancebetween the first portion 116 and second portion 118 in a directionparallel with the shafts that pass through the holes 122, 124. Thelateral dimension is also reflected in the distance between the firstportion 116 of the cover and the inner faces of the drive and drivenclutches 102, 101. These dimensions vary along the airflow path toimprove the air pressure at various points along the flow path. Thefront portion 116 has a deep region 132, followed by a ramp region 134,followed next by a shallow region 136. The deep region 132 has a largelateral dimension to permit air to enter at a relatively lower airpressure when compared to a conventional CVT cover with a uniformlateral dimension. The lateral dimension of the deep region 132 ispreferably between 70 and 100 mm. In one preferred embodiment, thedimension is approximately 90 mm. In the ramp region 134 the lateraldimension diminishes gradually until reaching the shallow region 136.The lateral dimension of the shallow region 136 is preferably between 50and 80 mm. In one preferred embodiment, the dimension is approximately65 mm. The ramp region 134 also widens in the transverse directionperpendicular to the lateral direction. The shallow region 136 beginsapproximately halfway between the first and second holes and continuesaround the outlet end 128 until reaching the outlet 114. In otherembodiments, the ramp region can begin nearer to the inlet 112 and endnearer to the outlet 114 for an even more gradual pressure change. Theslope of the ramp region is preferably approximately 0 to 20 degrees. Insome instances, the space constraints on the outside of the cover (othervehicle components that must be fitted) will dictate a hump in the rampor a certain angle. In any case, the cover is optimized to have theleast turbulence (e.g., the smoothest flow) through the flow path and tothe exit. This will maximize cool air flow with the least resistance toair entering the inlet port for the given constraints.

The cover 110 also includes a high region 138 that extends from the airoutlet 114 to the air inlet 112 on an upper side 131 of the cover 110. Aportion of the air in the cover moves from the shallow region 136 overthe high region 138 and around the driven shaft again before mergingwith the newly introduced airflow from the air inlet 112. A ridge 140separates the high region 138 from the deep region 132, the ramp region134, and the shallow region 136. The ridge 140 extends tangentially fromthe first hole 122 and reaches approximately to a midpoint of the secondhole 124. A portion of the high region 138 at a perimeter of the cover110 near the air inlet 112 is a divider 142 that directs air passingover the high region 138 back into the main airflow, and prevents theair from exerting outward pressure on the inlet air. The divider 142covers approximately half the distance between the cover shell 144 andthe first hole 122 measured in a radial dimension outward from the firsthole 122.

As the air enters the cover 110 from the inlet 112, the laterally widthdimensions of the flow path therefrom begin large and becomeprogressively smaller until the air exits the cover 110 at the outlet114. The effect of this structure is to reduce the pressure drop in theair when introduced to the cover 110 thereby improving efficiency.Conventional designs have an abrupt change in dimension, which causes alarger pressure spike, in turn requiring more pressure to maintainairflow through the cover 110. In some covers, the abrupt dimensionchange causes the internal air pressure to be large enough to cause airto blow back out of the inlet 112 hindering the efficiency of thecooling system.

FIG. 3 is an isometric view of a portion of a CVT cover 200 according toembodiments of the present disclosure in which the outlet is orienteddifferently relative to the cover 110. The cover 200 includes featuresgenerally similar to features of other covers described herein includingthe inlet 112, outlet 114, deep region 132, ramp region 134, shallowregion 136, high region 138, and ridge 140. The outlet 114 is atapproximately the 9 o'clock position relative to the second hole 124. Bycomparison, the outlet 114 of FIG. 2 is at approximately the 1 o'clockposition. The inlet 112 can similarly be oriented differently accordingto the dimensions of a given CVT. The cover itself can be made using amold or another suitable manufacturing technique. In some embodimentsthe cover has a uniform thickness throughout the cover.

In either of these preferred embodiments, the channeling of the coolingair creates less backpressure and more flow through of fresh air tobetter cool the clutches and belt.

FIGS. 4A-E illustrate various configurations of CVT cover air channelingstructures. In FIG. 4A the cover does not include air channelingstructures, other than an open, smooth case. In this instance asignificant amount of the air flow is recirculated back to the inlet.This recirculated air can create resistance to incoming air such thatthe flow of cool air into the cover is reduced. The recirculating air isalso warmer, thus reducing the clutch and belt cooling.

FIG. 4B shows a slightly modified cover with a diversion wall to directthe air out of the cover near the outlet and driven clutch (not shown inthis figure). The wall causes less recirculation and better air flowwith less resistance at the inlet and cooler air overall.

FIGS. 4C-E illustrate different structures near the inlet that affectflow. These structures may be used in conjunction with the exitstructures discussed above with reference to FIGS. 4A and 4B. FIG. 4Cincludes only a drop wall from the upper portion of the cover to thelower portion adjacent the inlet. Without a significant diversion forrecirculating air flow is not optimized. Thus, incoming air becomesturbulent as it enters the recirculating air flow path.

FIG. 4D includes a recirculating air flow diverter to channelrecirculating air above the main inlet flow path. Some turbulence occursbut flow is better than in 4C above.

FIG. 4E includes a larger diverter for the recirculating air. Thisarrangement puts the recirculating air in a laminar flow path with theentering air to create the best flow with the least resistance. Inalternate embodiments, the shield may be larger or smaller to achievedesired flow consistent with packaging and other design parameters.

While the preferred embodiments of the invention have been illustratedand described, as noted above, many changes can be made withoutdeparting from the spirit and scope of the invention. Accordingly, thescope of the invention is not limited by the disclosure of the preferredembodiments. For example, the present invention can include othermechanical equivalents that prevent an axle nut from loosening from theaxle, including a retaining arm extending from the axle nut to a singlelug or to another portion of the wheel. Other embodiments are alsopossible. Accordingly, the invention should be determined entirely byreference to the claims that follow.

The invention claimed is:
 1. An off-road vehicle for traversing asurface, comprising: surface engaging members; an engine that generatespower; a transmission coupled between the engine and the surfaceengaging members for transferring power from the engine to the surfaceengaging members; the transmission comprising: a drive clutch thatreceives at least a portion of the generated power from the engine, thedrive clutch being driven by an input shaft, the drive clutch having afirst side from which the input shaft extends and a second side oppositethe first side; a driven clutch that is offset from the drive clutch ina first direction of the vehicle, the driven clutch having an outputshaft to send power to the surface engaging members; a belt thattransmits at least a portion of the received portion of the power fromthe drive clutch to the driven clutch; and a clutch cover that covers atleast a portion of the drive clutch and at least a portion of the drivenclutch, the cover having a first side through which the input shaftextends and a second side opposite the first side of the cover, whereinthe cover includes: an air inlet on the first side of the cover adjacentthe drive clutch, an air outlet adjacent the driven clutch, a deepregion adjacent the air inlet, a shallow region adjacent the air outlet,and a ramp region defined between a ramp surface and the second side ofthe cover having a longitudinal dimension and a lateral dimension, thelateral dimension decreasing along an entirety of the longitudinaldimension in the direction of the deep region toward the shallow region.2. The vehicle of claim 1, wherein at least a portion of the ramp regionis a semi-circular region.
 3. The vehicle of claim 1, further includingan air channeling structure adjacent the air inlet.
 4. The vehicle ofclaim 1, further including a diversion wall adjacent the air outlet. 5.The vehicle of claim 1, wherein the cover further includes: a highregion that extends from the air outlet to the air inlet on the cover;and a ridge that separates the high region from the deep region, theramp region, and the shallow region.
 6. The vehicle of claim 5, whereinthe first side of the cover further includes: a first hole that receivesa drive shaft coupled to the drive clutch; a second hole that receives adriven shaft coupled to the driven clutch; and wherein the ridge extendsgenerally tangentially from the first hole towards an approximatemidpoint of the second hole.
 7. The vehicle of claim 5, wherein the highregion includes: a divider positioned at a perimeter of the first sideof the cover adjacent the air inlet, wherein the divider longitudinallyextends a portion of a distance between the perimeter of the cover andthe first hole.
 8. A vehicle comprising an engine and a transmission;the transmission comprising a drive clutch with a drive shaft and adriven clutch with a driven shaft, a cover at least partiallysurrounding the drive clutch and the driven clutch, the cover having afirst side and a second side, the cover comprising: a first hole adaptedto receive the drive shaft on the first side of the cover; a second holeadapted to receive the driven shaft on the first side of the cover; aninterior within which the drive clutch and driven clutch are positioned;at least one air inlet adapted to provide air from an exterior of thecover to the interior; and at least one air outlet adapted to provideair from the interior to the exterior; wherein the interior of the coverincludes: a deep region adjacent the air inlet on the first side of thecover, wherein the deep region includes a first lateral dimension; ashallow region adjacent the second hole and the air outlet, wherein theshallow region includes a second lateral dimension that is less than thefirst lateral dimension, wherein the deep region and the shallow regionform at least one portion of an airflow channel that guides air flowingfrom the at least one air inlet to the at least one air outlet; and aramp region that extends from the deep region to the shallow region, theramp region having a longitudinal dimension and a third lateraldimension that continuously decreases along an entirety of thelongitudinal dimension.
 9. The vehicle of claim 8, further comprising adiversion ridge extending adjacent at least a portion of the rampregion.
 10. The vehicle of claim 8, wherein the ramp region formsanother portion of the air channel, and the ramp region has a transversedimension that is substantially perpendicular to the third lateraldimension and that continuously increases along a longitudinal directionintermediate the deep region and the shallow region.
 11. The vehicle ofclaim 10, wherein a transverse slope of the ramp region is between 0degrees and 20 degrees.
 12. The vehicle of claim 8, further including afirst cover portion and a second cover portion that is separate from andlaterally offset from the first cover portion, and the first and thesecond cover portions are coupled together to form the interior.
 13. Thevehicle of claim 12, wherein each of the air inlet and the air outletare positioned entirely on the first cover portion.
 14. The vehicle ofclaim 13, wherein the first cover portion is laterally intermediate thesecond cover portion and the engine of the vehicle.
 15. The vehicle ofclaim 13, wherein the first cover portion being on the first side of thecover.
 16. The vehicle of claim 8, further including an air channelingstructure adjacent the air inlet.
 17. The vehicle of claim 8, furtherincluding a diversion wall adjacent the air outlet.
 18. A transmissionfor a vehicle that includes at least a drive shaft and a driven shaftthat is offset in a longitudinal direction, wherein each of the driveand the driven shafts extend in a lateral direction that is transverseto the longitudinal direction, and a vertical direction is transverse toeach of the longitudinal direction and the lateral direction, thetransmission comprising: a drive clutch held by the drive shaft; adriven clutch held by the driven shaft; and a case including: a firstlateral portion; a second lateral portion; an air inlet extendingthrough at least one of the first lateral portion of the case or thesecond lateral portion of the case; an air outlet extending through atleast one of the first lateral portion of the case or the second lateralportion of the case; and an airflow channel within the case that guidesat least a portion of flowing air from the air inlet downstream to theair outlet, wherein the airflow channel has a deep region that isdownstream from the air inlet and upstream from the air outlet, a rampregion that is downstream from the deep region and upstream from the airoutlet, and a shallow region that is downstream from the ramp region andupstream from the air outlet, the ramp region extending from the deepregion to the shallow region, the ramp region defined between a rampsurface and the second lateral portion of the case having a longitudinaldimension and a lateral dimension, the lateral dimension decreasingalong an entirety of the longitudinal dimension in the direction of thedeep region toward the shallow region.
 19. The transmission of claim 18,wherein each of the air inlet and the air outlet extend through thefirst lateral portion of the case.
 20. The transmission of claim 18,wherein the case further includes a drop wall extending from an upperportion of the first lateral portion to a portion of the deep regionthat is substantially adjacent the air inlet.
 21. The transmission ofclaim 18, wherein a lateral dimension of the deep region is greater thana corresponding lateral dimension of the shallow region and a verticaldimension of the deep region is less than a corresponding verticaldimension of the shallow region.